Antiplugging agents for hydroxy stearate greases



cation systems. calcium, lithium, or calcium-lithium hydroxy stearateUnited States Patent Office 3,1 7 1,8 12 Patented Mar. 2, 1 9653,171,812 ANTIPLUGGING AGENTSFOR HYDROXY STEARATE GREASES Alcide C.Horth, Sarnia, Ontario, and Warren C. Pattenden, Mooretown, Ontario,Canada, assignors to Esso Research and Engineering Company, acorporation of Delaware No Drawing. Filed July 25, 1 960, Ser. No.44,857 5 Claims. (Cl. 252-40) This invention relates to metal hydroxystearate grease compositions adapted to be dispensed by centralizedlubri- Particularly, the invention relates to greases containing a smallamount of additive to prevent plugging of small diameter feed lines incentralized lubrication systems.

Calcium, lithium and mixed calcium-lithium hydroxy stearate greases arewell known in the art and in general, have excellent shear stability andnon-bleeding characteristics. However, when these greases are subjectedto forced feeding under high pressure through narrow diameter orificesor lines such as are encountered in centralized lubrication systems,there is a tendency for the grease to form hard solid deposits whichplug the feed lines of the system. It has been found that by theaddition of a small amount of certain agents to the grease, that itsresistance to plugging is greatly increased.

The antiplugging agents found particularly useful are water, glycerine,and polyalkylene glycols such as polyethylene glycol of 200 to 7,000,preferably 700 to 3,000

molecular weight. It has been further found that a combination of 0.5 to1.0 part by weight of water per part by weight of glycerine is moreeffective than a like amount of either water or glycerine. While thesematerials have been previously used in greases, it is believed thattheir use and mode of use in the hydroxy sterate greases of theinvention is new.

Thus, water has been previously used in low temperature grease systems,particularly in simple calcium soap grease, in order to give the greasea fibrous nature and hold it together. One advantage of the hydroxystearate greases, particularly calcium hydroxy stearate greases, is thatwater is not necessary for this purpose, since the hydroxy portion ofthe molecule acts as a linking agent and imparts fibrousness to thegrease. As a result, hydroxy stearate greases in practice are completelydehydrated during preparation and it is unconventional to form afinished IZ-hydroxy stearate grease containing free water.

Glycerine and polyalkylene glycols are known as structure modifiers.Thus, Bondi, in US. Patent 2,475,589, describes the addition ofglycerine, polyalkylene glycols and naphthenates to greases thickenedwith a mixture of soaps of hydroxy stearic acid and hydrogenated fishoil fatty acids to minimize bleeding and improve shear stability.However, calcium, calcium-lithium or lithium 12-hydroxy stearate greases(absent the fish oil acid soap) do not require structure modifiers astaught by Bondi. In addition, while Bondi had his additives presentduring the cooling operation, i.e. present in the melted grease, theprocess of the present invention preferably involves adding theadditives to a cold or slightly warm grease. By this latter method, theloss in hardness (i.e. yield) and color degradation which frequentlyoccurs when glycerol and polyalkylene glycols are present in grease athigh temperatures is avoided.

The grease compositions of this invention will therefore comprise amajor amount of lubricating oil, about 5 to 30, preferably 5 to 15 wt.percent of a metal hydroxy stearate and about 0.1 to 3.0, preferably 0.2to 1.0 wt. percent of antiplugging agent.

The metal component of the hydroxy stearate can be lithium or calcium ora mixture thereof. v i

The lubricating oil is preferably a mineral lubricating oil althoughsynthetic oils such as dieste'rs may be used.

Conventional additives can also be'added, including oxidation inhibitorssuch as phenyl-alpha-naphthylamine; rust preventives such as sodiumnitrite; t ackiness agents such as polyisobutylene, dyes, auxiliarythickeners and thelike.

The antiplugging additives can be-simply added to the finished greasecomposition by mixing. Preferably, these additives are added during thecooling cycle of the preparation of the grease, i.e. attcmperaturesbelow the melting point of the hydroxy stearate soap,-"e.g.below 200 F.

A'Trabon centralized lubrication system was used in order to test theplugging characteristics of the greases of the invention. This systemincluded a pump circulating the grease from a reservoir through smalldiameter feed tubes and back to the reservoir. "The number of hours ofoperation before plugging of the system was determined.

The invention will be further understood by reference to the followingexamples which include a preferred form of the invention.

Example I Two base greases were used in the experiments: Grease Aconsisted of mineral lubricating oil thickened with 9 wt. percent ofcalcium-lithium 12-hydroxy stearate thickener in a weight ratio ofcalcium hydroxy stearate to lithium hydroxy stearate of 4:1. Grease Bconsisted of mineral lubricating oil thickened with 8.7 wt. percent ofcalcium 12-hydro-xy stearate and containing about 9.25 wt. percent ofextreme pressure additives. To these greases were added varying amountsof water, glycerine and polyethylene glycol of 1500 molecular weight.This addition was made by simply mixing the water, glycerine orpolyethylene glycol into the grease at room temperature. Thecompositions were then tested in the centralized lubrication systempreviously described above and the time required for plugging of thissystem recorded. The compositions tested and the results obtained aresummarized in the following table:

EFFECT OF ANTI-PLUGGING ADDIIIVES ON GREASE PERFORMANCE IN A TRABONCENTRALIZED LUBRI- CATION SYSTEM As seen by the preceding table, water,glycerine and polyethylene glycol were all effective in preventingplugging. The maximum pressures upon the grease during testing in theTrabon lubricator were about 2500 p.s.i.g., while the smallest orificesthrough which the grease was passed were about & inch diameter.

In sum, the present invention relates to calcium, lithium andcalcium-lithium greases prepared from 12-hydroxy stearic acid andcontaining a small amount of antiplugging agent. This grease isparticularly adapted for use under high pressures, e.g. 500 to 5,000p.s.i.g., and in small diameter lines, e.g. to A inch lines or orifices.

"Whatis lclai niedaiszk .1 t.

.1.,Atlubricating grease-s11itab1e. for use in centralized lubricationsystems under high pressure comprising a major amount of minerallubricating oil, about 5 to 30 percen t of a g rea se. thickenerconsisting essentially of metal hydroxy stearate, and'about 0.1- to 3.0wtsperce'nt of a. material selected f romthe group consistingotglycerine, polyethyleneglycol of fl 0()to' 7,000. molecular weight, andmixturesl consisting of water and glycerine in a, weight ratio: of from0.5-,1.0:1, Wherein said metal is selectedfrom the group consisting ofcalcium, and mixtures of ca1ciurn and,lithium=wherein said'calciurn ispresent in a major molar amount and wherein-.- all of .said materialwhich is presen-t-wasdadded to a'mixture of said oil and saidstearate-atga temperaturerbelow=200 F. 2.v .-A grease compositionaccording to claim 1, wherein sai d rnaterial is glycerine.;; I

3. A greasecornposi on according to claim 1, wherein said material is a,mixtureof water and glycerine.

, 4 A greasecomposition -accord-ing to claim- 1, wherein said materialis polyethylene glycol of,700 to. 3,000 molecularweight. I Y

e i '4 a the amount of said metal hydroxy stearate is 5 to 15.0 wt.percent, the amount- 0f said'material is 0.2 to- 1.0 wt.

percent and said metal consists of calcium.

References Cited in the file of this patent UN TED T TES A NT 2,607,734Sproule'et a1 Aug. 19, 1952 2,846,394 Brunstrum et al. Augi'fi, 19582,898,298 Zweifel etal; Aug. 14, 1959 2,929,782. Sproule et a1. Mar. 22,1960 FOREIGN PATENTS I 134,363 Australia Sept..21, 1947 Canada July 21,1959 579,995 t OTHER REFERENCES I The Manufacture and Application ofLubricating Greases,-Boner;, Reinhold Publication Corp., New York I 5. Alubricating grease accordingyto"claim wherein (1 954), pages43-44? l j

1. A LUBRICATING GREASE SUITABLE FOR USE IN CENTRALIZED LUBRICATIONSYSTEMS UNDER HIGH PRESSURE COMPRISING A MAJOR AMOUNT OF MINERALLUBRICATING OIL, ABOUT 5 TO 30 WT. PERCENT OF A GREASE THICKENERCONSISTING ESSENTIALLY OF METAL HYDROXY STEARATE, AND ABOUT 0.1 TO 3.0WT. PERCENT OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OFGLYCERINE, POLYETHYLENE GLYCOL OF 700 TO 7,000 MOLECULAR WEIGHT, ANDMIXTURES CONSISTING OF WATER AND GLYCERINE IN A WEIGHT RATIO OF FROM0.5-1.0:1, WHEREIN SAID METAL IS SELECTED FROM THE GROUP CONSISTING OFCALCIUM, AND MIXTURES OF CALCIUM AND LITHIUM WHEREIN SAID CALCIUM ISPRESENT IN A MAJOR MOLAR AMOUNT AND WHEREIN ALL OF SAID MATERIAL WHICHIS PRESENT WAS ADDED TO A MIXTURE OF SAID OIL AND SAID STEARATE AT ATEMPERATURE BELOW 200*F.